Gas turbine engines are generally known for use in a wide range of applications such as aircraft engines and auxiliary power units for aircraft. In a typical configuration, the gas turbine engine includes a turbine section having a plurality of sets or rows of stator vanes and turbine blades disposed in an alternating sequence along an axial length of a hot gas flow path of generally annular shape. The turbine blades are coupled to a main engine shaft through one or more rotor disks. Hot combustion gases are delivered from an engine combustor to the annular hot gas flow path, resulting in rotary driving of the turbine rotor disks which, in turn, drives the compressors and gearbox.
Advanced high performance gas turbine engines, such as high pressure turbines (HPTs) are constantly driven to achieve maximized thermodynamic efficiency, which is generally achieved by operating at higher rotor speeds and temperatures. In many gas turbine engine configurations, especially for HPTs, the turbine blades are mounted at the periphery of the one or more rotor disks through a mechanical connection, e.g., through a dovetail-type connection or the like. However, the mechanical properties of the rotor disks and turbine blades may be inadequate to sustain induced loads during operation, even with selection of special materials and engineered cooling schemes. This may be especially true as efforts are made to maximize thermodynamic efficiency by maximizing rotor speeds and operating temperatures.
One approach taken to maximize temperatures and load carrying capability in turbine blades and rotor disks, particularly in HPTs is to employ dissimilar materials for the rotor disks and the turbine blades while removing the stress concentrations associated to mechanical connections. The respective rotor disks and turbine blades, including the dissimilar materials, are directly bonded together as opposed to relying upon a mechanical connection. In one example, the turbine blades may be operatively connected to blade mounts, e.g., by casting the turbine blades and blade mounts together, or by brazing or welding the turbine blades to the blade mounts. The blade mounts may be operatively connected to each other forming a blade ring, such as by casting a plurality of blade mounts together or by brazing or welding blade mounts together. However, the creation of an integral bonded rotor requires the release of hoop stress attributable to the thermal gradients and rotation of the rotor disk. The hoop stress can be broken by slotting the blade ring and rotor disk after bonding the blade ring and rotor disk together.
In addition, it is often desirable to regulate the normal operating temperature of certain turbine components in order to prevent overheating. That is, while engine stator vanes and turbine blades are specially designed to function in the high temperature environment of the mainstream hot gas flow path, other turbine components such as the rotor disks are not generally designed to withstand such high temperatures. Accordingly, in many gas turbine engines, the volumetric space disposed radially inwardly or internally from the hot gas flow path includes a fore seal plate, and an aft seal plate is also generally disposed on an opposite side of the turbine wheel from the fore seal plate. The fore and aft seal plates form respective fore and aft rotating internal engine cavities around the rotor disk(s). The internal engine cavities are sealed from direct contact with the high temperature environment of the mainstream hot gas flow path, sometimes with a cooling air flow provided therethrough. When provided, the cooling air flow is normally obtained as a bleed flow from a compressor or compressor stage forming a portion of the gas turbine engine. The internal engine cavities enable a normal steady state temperature of the rotor disks and other internal engine components to be maintained at or below a temperature of the high temperature environment.
With bonded turbine blade/rotor disk configurations that are slotted to relieve hoop stress, sealing of the internal engine cavities is often imperfect, resulting in excessive intrusion of high temperature gas from the mainstream hot gas flow path into the internal engine cavities or an excessive use of parasitic cooling air. While attempts have been made to seal the internal engine cavities, the configuration of the slots can complicate complete sealing using seal plates.
Accordingly, it is desirable to provide turbine wheels, turbine engines including the turbine wheels, and methods of forming the turbine wheels having improved seal plate sealing for bonded turbine blade/rotor disk configurations. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background.